1. Field of the Invention
The invention relates to nucleic acid probes and to methods for preparing nucleic acid probes.
2. Description of the Related Art
The bisulfite ion-catalyzed displacement of the C4 amine of a cytosine base with 1,2-ethylenediamine is a widely used reaction for the conversion of an unreactive C4 cytosine amine into a reactive aliphatic amine. The resulting aliphatic amine has been used to label DNA with suitable markers or reporter groups, such as fluorophores, chromogens, haptens, proteins, and so on. In addition, the reaction has also been used for the conversion of cytosine residues into uracils and thymidines.
Despite its widespread use, the reaction suffers from several disadvantages. For instance, the bisulfite activation step is very slow and inconvenient, taking place over several days. Further, the linker on the distal amine is generally of limited length, which can interfere with the hybridization process, resulting in depression of the sensitivity of the probe. In addition, because the modified reporter must present an electrophilic group, such as active ester or an isocyanate, competing reactions with water can depress yield, and result in the number of desirable reporter groups being too small to provide efficient signal generation.
Microwave energy has been used to accelerate chemical reactions in synthetic organic chemistry. Microwave energy has not been previously used, however, in biochemical reactions involving modification of nucleic acids, antibodies, enzymes, other proteins, or lipids.
In view of the disadvantages discussed above, and other disadvantages, a need exists for new nucleic acid probes, and for improved methods of preparing nucleic acid probes.